1. Related Art
The present invention relates to a method and apparatus for the termination of a cable of the external telecommunications network at customer premises, with particular reference to termination of optical fibres in the context of bringing fibre to the home (FTTH).
Public switched telecommunication networks currently comprise an access network of cables routed through various exchanges, which ultimately terminate on the distribution side in premises of commercial, industrial, or consumer customers. These cables are typically terminated on network termination points (NTEs) located at the customer's premises. Historically these cables have been twisted copper pairs, but increasingly there is a migration to FTTH to provide customers greater bandwidth for communications purposes.
Most of the customers connected to the access network by optical fibre are commercial entities. The significant cost of obtaining optical connection has, up to recent times, discouraged private or residential takeup. Moreover, the obtrusiveness of current optical network termination (ONT) equipment required to support the fibre connection—usually unimportant in an industrial or commercial environment, where it is usually hidden away in a dedicated communications room—would not sit well in a residential context. As prices start falling however, demand for FTTH is growing.
Currently, in a copper-based system, it is the practice to connect residential customer premises for telecommunications only after construction of the premises. The process typically involves the following steps: a cable from the access network terminating near to a customer's premises is led from a primary cross connection point located in a street cabinet, either by overhead or underground feed, to the wall of the premises. A hole is drilled through the fabric of the wall to allow the arriving cable access to pass into the premises. The cable passes into the interior of the premises, and is terminated at an NTE (such as, in the UK, an NTE5 master linebox). As its name suggests, the NTE typically marks the legal extent of the authority and responsibility of the external network service provider (such as British Telecommunications pIc in the UK). Such termination boxes cover the raw access hole on the interior wall, are either surface- or flush-mounted, and include a socket on the faceplate for compatible connector plugs such as a BT431 connector for telephones.
The surface-mount boxes tend to abut about 36 mm from the wall and are generally bulky and aesthetically displeasing. They are also susceptible to accidental or malicious damage as they can be knocked against and dislodged. The flush-mounted boxes need to be used with a compatible back box. However these are more time-consuming to install than surface-mounted boxes, as the wall surface will need to be broken to create a suitable cavity to accept the back box.
The present methods of installing a copper wire termination point therefore suffer from the need to destroy the building fabric of the premises by creating access for the entering external cable. NTEs are either unattractively bulky and thus unsuitable particularly in residential settings, or else are installed by further modification to the building infrastructure and at considerable cost, expertise and inconvenience.
Accessibility problems arise from the current method of locating NTEs on the interior walls of premises. The external network service provider needs to arrange appointments with the customer to gain access to the premises to install the connection, or to carry out other work related to the termination point, such as maintenance work, testing, or the making of replacements. This is a significant problem, caused by the busy and conflicting schedules of the external service provider and the householder. Service providers will seek to carry out their work mainly during office hours, the time during which working customers will not be at home. If schedules fail to match—which may occur in spite of appointments made for specific timeslots due to factors outside the parties' control—much time is lost and the financial cost of re-scheduling and re-making the visit is considerable. Valuable commercial goodwill is also lost in the process, which is of particular significance in an open telecommunications market.
One solution is to provide NTEs on the exterior of the premises. This is a common practice in the United States. While this solution does allow the external network service provider ready access to the NTE and the termination point, this location of equipment is vulnerable to damage—environmental, accidental and malicious. The NTE housing has to be made very strong to protect its contents—this has an impact on its cost and its size. Moreover, the relocation of the housing for the equipment from the inside of the premises to the outside may not necessarily improve the aesthetics of the premises—which is especially relevant in the case of residential properties. As described more fully below, the increased fragility, cost and size of an optical network termination (ONT) may make it unsuitable for such a vulnerable location outside of the premises.
There is yet another issue concerning accessibility to the network termination point. In the UK and many other countries, the days when a single service provider would supply a customer everything, from access to the network to the telephone in the sitting room, are gone. Customers are now free to tailor their own internal communications needs. The problems experienced by service providers has been discussed; customers should not experience the same problems with access to externally-located NTE, but other issues may arise, such as safety concerns, e.g. the risk of customers looking directly at a plug end and the associated laser hazard, which might arise if they have access to the fibre equipment arriving from the access network.
The above issues relate in the main to copper-based systems, but are not exclusive to them. The problems are further compounded with the advent of FTTH. This is due to the delicate nature of the ONT equipment, as well the sensitivity of optical fibre joins to misalignment, dust and the like. (In this description, references to “fibre unit” shall include individual fibre members as well as fibre bundles comprising a number of fibre members.)
Unlike copper wires, optical fibre has an inherent minimum bend radius which cannot be exceeded without risk of physically damaging the fibre unit or adversely affecting the performance of the fibre. A bare optical fibre comprising just the core, cladding and primary buffer has a minimum permissible bend radius typically of about 60 mm. A fibre cable including its outer protective layers, and bundles of optical fibre have even greater minimum permissible bend radii. Housing for fibre need to be dimensioned accordingly to accommodate the bend.
Furthermore, there is likely to be more equipment supporting the optical connection to the premises—such as a power supply for the equipment, Ethernet cables, co-axial cables, and the like—than is necessary with copper connections. All this means that the overall size of the housing for equipment for FTTH will be even bulkier—and even more of an eyesore and prone to damage—than today's copper-based NTEs already are, whether located within or external to the premises.
A further issue arising in the UK is the drive by Ofcom (the regulator and competition authority for communications industries in the UK) for open access to networks, to lead to greater competition between service providers. The applicants anticipate that in this climate, the network termination point will need to be precisely defined to clearly demarcate the limit of the access network service provider's extent of responsibility. The communications market is moving away from the days when the access network service provider supplied everything up to and including the telephone.
Present methods to terminate optical networks have ONTs located in the same positions as those used for copper-based NTEs, namely on the interior wall of the premises, or externally to the premises. The problems experienced by NTEs are exacerbated by the increased size of the housing required by the ONT equipment, the fragility of the optical fibre and any splices or connections providing the connection.
For all the above reasons, it would be desirable to have a solution to address the problems associated with locating the termination point for the access network on the inside of premises, or externally of the premises.